c) Why is it necessary to filter off the zinc before the second titration takes place?
If you titrated the iron (II) against manganate to oxidise it to iron (III), the zinc would reduce it straight back to iron (II). That would then have to be oxidised by more managante and there'd be an endless cycle. So you'd need an infinite quantity of manganate and never reach an end point.
is this correct?
Last, Kc, at high temperature the value is high and when the temperature lowers the Kc value increases more, does this mean the reaction is exothermic? but does it mean the forward reaction is exo? but I thought that Kc decreases if forward temp is exothermic